Stitch forming mechanism for sewing machines



R. J. oss

STITCH FORMING MECHANISM FOR SEWING MACHINES Filed Aug. 50, 1965 3 Sheets-Sheet 1 INVENTOR. Roger J. Ross "A7? TORNEY WITNESS Jan. 30, 1968 R- J. ROSS STITCH FORMING MECHANISM FOR SEWING MACHINES Filed Aug. 30, 1965 3 Sheets-Sheet 2 WITNESS g5 1 z w Fig.3. B

INVENTOR Roger J. Ross Y ATTORNEY Jan. 30, 1968 R. J. ROSS v STITCH FORMING MECHANISM FOR SEWING MACHI INES Filed Aug. 30, 1965 3 heets-Sheet 3 INVENTOR.

Roger J. Ross WITNESS Q 7 BY ewzw hi United States Patent 3,365,082 STITCH FORMING MECHANISM FOR SEWING MACHINES Roger J. Ross, Dover, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 30, 1965, Ser. No. 483,696 9 Claims. (Cl. 112-193) ABSTRACT OF THE DISCLOSURE A lockstitch sewing machine is disclosed having a loop taker journaled in a supporting arm pivoted in the machine frame at a point remote from the loop taker. Actua'ting mechanism is provided for simultaneously oscillating both the loop taker and the supporting arm so as to impart an epitrochoidal path of motion to the loop seizing beak and to the bobbin thread guiding means on the loop taker. A braking device for preventing overspinning of the bobbin is relieved at stitch setting by the tension of the bobbin thread.

This invention relates to sewing machines and more particularly to novel and advantageous instrumentalities for forming lock stitches.

It is an object of this invention to provide lock stitch forming instrumentalities capable of being actuated by simple reciprocating motion and effective to produce thread concatenation into lock stitches in a superior fash- 1011.

An object of this invention is to provide a novel loop taker for a lock stitch sewing machine which, in response to reciprocatory actuation in simple harmonic motion, imparts to the needle loop seizing beak a curvilinear motion which is particularly advantageous in that it effects concatenation of the sewing threads very early during each stitch forming cycle leaving ample time for the take-up action necessary to set stitches into a work fabric.

It is an object of this invention to provide a shuttle mechanism for a lock stitch sewing machine in which the loop seizing beak of the shuttle is arranged to partake of a novel trochoidal path of motion in attaining the aforesaid advantages.

It is also an object of this invention to provide a loop taker of the above character is which the bobbin thread issues from a guide means on a bottom casewhich is arranged to partake of an epitrochoidal path of motion differing from that of the loop seizing beak and by which difference in paths of motion an advantageous control of the bobbin thread is attained during stitch formation.

A further object of this invention is to provide a novel means for preventing overspinning of the bobbin during stitch formation.

With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. 1 represents a side elevational view of a sewing machine embodying this invention.

FIG. 2 represents a bottom plan view of the sewing machine of FIG. 1,

1G. 3 is a perspective View of the actuating mechanism of the sewing machine of FIG. 1 and including the needle and loop taker mechanisms thereof,

FIG. 4 represents an enlarged top plan view of a portion of the loop taker mechanism including the needle and the needle and bobbin-threads as the loop taker is about to seize a needle thread loop,

FIG. 5 is a side elevational view of the loop taker in the needle loop seizing position of FIG. 4 and including a representation of the needle with sewing threads concatenated into a work fabric together with the work support and the loop taker support illustrated in cross section taken substantially along line 5-5 of FIG. 4,

FIG. 6 represents a top plan view of a portion of the loop taker mechanism including the needle and bobbin threads during manipulation of a needle thread loop by the loop taker,

FIG. 7 represents a top plan view of a portion of the loop taker mechanism together with the needle and bobbin threads in the position which the loop taker occupies at the setting of a stitch, and including a quasi-diagrammatic representation of the previously formed stitches,

FIG. 8 is an enlarged cross sectional view of the shuttle including the bobbin and the bobbin thread taken substantially along line 88 of FIG. 7, and

FIG. 9 is a top plan view of the loop taker and the supporting arm therefor at one extremity of oscillation of the supporting arm and illustrating in broken lines the path of motion of the loop seizing beak and the bobbin thread delivery guide means of the bobbin case.

Referring to the drawings, the sewing machine to which the loop taker of this invention is applied includes a frame comprising a bed plate 11 to which a depending wall 12 is secured at one free extremity and a pair of depending legs 13 are secured at the other extremity. Rising from the bed plate is a unitary supporting plate, indicated generally as 14, which includes a standard 15, a bracket arm 16 cantilevered over the bed plate, and a head portion 17.

I Journaled transversely in the supporting plate near the junction of the standard and the bracket arm is an operating shaft 20 which carries an eccentric 21 from which actuation of all of the operating mechanism of the sewing machine is derived. A balance wheel 22 may be carried on the shaft 20 at the front of the machine and a pulley or other suitable connection to a source of power (not shown) may be carried by the shaft at the rear of the machine.

For operating the stitch forming instrumentalities, a bell crank lever 30 is fulcrumed on a shouldered screw 31 threaded into the supporting plate 14. The bell crank includes an arm 32 extending alongside the bracket arm 16 and an arm 33 depending alongside the standard. An aperture 34 in the arm 33 accommodates the drive eccentric and is preferably formed with spaced outturned ears 3 5 which embrace diametrically opposite sides of the eccentric.

At the free end of the bell crank arm 32 is pivoted a depending link 36 pivotally connected, in turn, to a needle bar 37 of rectangular cross sectional shape endwise slidable in a vertical slot 38 formed in the head 17. A needle clamp 39 on the needle bar serves to secure a conventional needle therein.

A block 41 secured by screws 42 to the head 17 is formed with a gib 43 which overlies the slot 38 to constrain the needle bar in the slot 38. The block 41 also carries a needle thread tensioning device 44 and a bracket 45 on which is carried a thread guide 46 and alight thread tensioning device 47.

The needle thread take up is provided by a take up lever 50 fulcrumed on a shouldered screw 51 which passes through a clearance slot 52 in the bell crank lever 30. A roller 53 secured on the take up lever enters a slot 54 formed on the bell crank arm 32 so as to be driven in response to oscillation of the bell crank. At the free extremity the take up lever is formed with a thread engaging loop 55. The needle thread is thus directed from a spool on a spool pin 56 on the supporting an aperture covered by a throat plate 61 which is formed with a needle aperture 62 and with slots 63 for a feed dog indicated at 64 in FIG. 2. The work feeding mechanism may be of any known variety such as the drop feed mechanism illustrated in the drawings. Since the feed mechanism does not form a direct part of this invention it will not be described herein with further particularity. The feed dog 64 is opposed above the throat plate 61 by a conventional presser foot 65 secured on an endwise shiftable spring biased presser bar 66 carried in the sewing head 17.

Referring particularly to FIGS. 2, 3 and 5, the loop taker of this invention takes the form of a circularly moving shuttle indicated generally at 70. The shuttle 70 is journaled for turning movement in an upwardly open counterbore 71 formed in an oscillating arm 72 fulcrumed on a shouldered screw 73 threaded beneath the bed plate 11. A shuttle driver 74 is carried within the counterbore 71 beneath the shuttle and is fast on a shaft 75 journaled in a bore 76 concentric with the counterbore 71 and through the oscillating arm 72. Beneath the oscillating arm 72 a pinion 77 is secured as by a set screw 78 to the shuttle driver shaft 75.

Carried beneath the oscillating arm 72 is a plate 80 formed with an arcuate gear segment 81 arranged in mesh with the pinion 77. During sewing the plate re mains stationary relatively to the sewing machine frame being secured in position by the fulcrum screw 73 for the oscillatory lever 72 and also by a clamp screw 82 threaded beneath the bed plate 11 and passing through a slot 83 in the plate 80. By loosening the camp screw 82 the position of the plate 80 may be adjusted to effect adjustment of the turning of the shuttle relatively to the reciprocation of the needle, for optimum loop taking effectiveness.

Actuation of the loop taker is accomplished from oscillatory movement of the bell crank 30 in response to the eccentric 21 by a roller carried by the depending bell crank arm 33, the roller 90 is embraced by inturned ears 91 formed on a lever 92 fulcrurned on the standard 15 by means of a shouldered screw 93. At the opposite side of the fulcrum, the lever 92 is pivotally connected by a fastening 94 to a link 95 which is in turn pivotally connected by a screw 96 to an ear 97 struck downwardly from a slide plate 98. The slide plate 98 is constrained in a slot 99 beneath the bed plate by a gib 100 and is formed with a second struck down ear 101 to which is pivotally connected by a screw 102 a link 103 which is pivoted on a screw 104 beneath the oscillatory arm 72.

Referring to FIGS. 4 through 9, in which are illustrated the details of construction of the loop taker, the shuttle 70 comprises an upwardly open cylindrical basket with a bottom wall from the center of which basket rises a stud 112. Formed about slightly more than half the periphery of the basket 110 is an arcuate bearing rib 113 which is journaled snugly in the counterbore 71 of the supporting arm 72 and which is formed at one extremity with a loop seizing beak 114. As illustrated in FIGS. 4, 6, and 7 the cylindrical basket 110 is offset slightly relatively to the center of curvature of the annular bearing rib 113 so that the cylindrical basket 110 will similarly be slightly eccentric to the axis of the shaft 75. The counterbore 71 extends to the free extremity of the supporting arm 72 providing an opening 115 in passage through which the loop seizing beak 114 may seize a needle thread loop. A gib 116 secured by screws 117 over the supporting arm overlies the shuttle bearing rib 113 to constrain the shuttle therein.

The shuttle driver 74 is formed with an arcuate rib 120 which extends between the extremities of the shuttle bearing rib 113 thus to impart oscillatory motion to the shuttle about its central axis as the pinion 77 is turned in mesh with the gear 81. The shuttle ,in addition, is carried bodily by the supporting arm 72 for oscillatory motion about the supporting arm fulcrum 73. The resulting motion of any point on the shuttle is epitrochoidal. In particular, the path of motion of the loop seizing beak 114 of the shuttle, since it is disposed at a larger radius than the pinion 77 will partake of a prolate epitrochoidal path as illustrated by the dashed line A in FIG. 9. An advantage of this novel loop taker motion resides in the ease and speed with which needle thread loops are seized, manipulated completely about the shuttle, and shed from the shuttle. Indicated at in FIG. 9 is the loop seizing point along the path of motion of the loop seizing beak, and indicated at 126 is the point along the path of motion of the beak at which the needle thread loop will have been carried completely about the shuttle. Beyond the point 126, the shuttle beak will no longer influence the needle thread loop and the take up will assume its role of drawing up the thread. Moreover, the take up will not be required to draw the shed needle thread loop about a shuttle as in shuttle constructions which turn about a fixed axis since the shuttle basket 110 will continue movement toward the right as illustrated in FIG. 9 and out of the needle thread loop. Since the take up will thus draw up a thread loop which is largely free of the shuttle, the take up motion necessary to complement the loop taker of this invention is less critical than most prior art take ups which must take up the thread loop in accurately metered amounts to match those given by the shuttle as the thread loop passes thereover. In the drawings FIGS. 4 and 5 illustrate the shuttle with the beak positioned substantially at needle thread loop seizure corresponding to the point 125 in FIG. 9. FIG. 6 illustrates the shuttle with the beak 114 positioned substantially at the needle thread shedding point 126 as illustrated in FIG. 9. FIG. 7 illustrates the shuttle at the extreme position of motion with the beak corresponding to a point 127 in FIG. 9.

FIGS. 5 and 8 best illustrate the bobbin 130 and the provision for controlling the bobbin thread tension. The bobbin 130 comprises a plain bottom flange 131 and a central hub 132 formed with a blind bore 133 accommodating the stud 112 within the shuttle basket 110. A top flange 134 of the bobbin is formed with an annular recess 135 of which the inner diameter is undercut as at 136 to provide a fingernail grip for removing and replacing the bobbin in the basket.

For accommodating the bobbin thread, the shuttle basket 110 is formed with a thread slot 140 leading from the upper edge of the basket to a thread eyelet 141 near the bottom wall 111 of the shuttle. Above the eyelet 141 the shuttle basket is formed with a recess 142 from which a thread guiding groove 143 extends to the upper edge of the basket 110. Pivoted on a pin 144 on the side of the shuttle basket is a bobbin brake lever 145 of which a lower arm 146 depends into a slot in the shuttle base in position contiguous to the rim of the bottom flange 131 of the bobbin. An upper arm 147 of the brake lever underlies the thread guiding groove 143 and is further provided with a lateral finger 148 across which the bobbin thread is directed between the eyelet 141 to the thread guiding groove 143. Secured by a screw 149 to the exterior of the shuttle basket 110 is a leaf spring of which an upper arm 150 extends across the upper arm 147 of the brake lever and across the thread slot 140, and a lower arm 151 extends opposite the lower arm 146 of the brake lever. The action of the spring arm 151 braces the brake lever arm 146 against the bottom bobbin flange to deter overspinning of the bobbin. In addition the bobbin thread in passing between the upper arm 147 and the spring arm 159 will be subjected to a tensioning friction. When, however, the bobbin thread is drawn taut diametrically across the bobbin from the thread guiding groove 143 as in the extreme position of the shuttle as illustrated in FIG. 7, the bobbin thread will apply a counterclockwise turning movement to the brake lever 145 as viewed in FIG. 8 and release both the bobbin thread tension and braking influence on'the bobbin.

Such'bobbin'thread tension release occurs automatically after each stitch has been set and provides a limit on the stitch setting tension applied to the bobbin thread. When the bobbin thread tension is thus released, an increment of bobbin thread equal to that used in forming the preceding stitch may be withdrawn from the bobbin free of influence of the bobbin thread tensioning means, and moreover, without adversely influencing the preceding set stitch.

. In dot and dashed line in FIG. 9 labeled B is indicated the path of motion of'the thread guiding groove 143 on the shuttle basket 110. Due to the eccentricity of the shuttle basket the path B takes the form of a modified prolate epitrochoid. It will be apparent from the path of motion B illustrated in FIG. 9 that a considerable degree of control is exercised over the position of the stack bobbin thread while the shuttle occupies positions other than the stitch setting "position of FIG. 7 i.e., since the thread guiding groove 143 partakes of the prolate epitrochoid loop denoted at 160 in FIG. 9, the slack bobbin thread will be partly taken up during stitch formation, and moreover, such slack bobbin thread by 'virtue of this advantageous motion will be urged away from the path of the needle.

Although in the preferred embodiment illustrated in the accompanying drawings, the shuttle 70 is journaled in a pivotally mounted supporting arm 72 and the pinion 77 associated with the shuttle meshes with an arcuate gear segment 81 giving rise to epitrochoidal paths of motion of the loop seizing beak 114 and the bobbin thread guiding groove 143, it will be appreciated that the shuttle supportingarm 72 may be made slidable on a straight track and the gear segment 81 may correspondingly take the form of a straight rack in which case the paths of motion of the loop seizing beak 114 and the bobbin thread guiding groove will be trochoidal.

The loop taker of this invention as represented by the selected embodiment described above provides for the formation of lock stitches by a novel loop taker which may be actuated from a reciprocatory element moving in a relative short stroke. The movement imparted to the shuttle in a novel epitrochoidal path provides for rapid thread concatentation with ample time for thread take up action in stitch setting. The epitrochoidal path of motion of the shuttle also provides for an advantageously controlled slackness in the bobbin thread during thread concatenation with the bobbin thread drawn taut for stitch setting and thereafter automatically released from tension as a fresh increment of bobbin thread is drawn from the bobbin.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a sewing machine having a frame, a thread carrying needle endwise reciprocable in said frame, an actuating mechanism carried in said frame and operably connected to impart reciprocatory movement in an endwise path to said needle, a loop taker supporting arm pivotally mounted in said frame for oscillatory movement transversely of said path of needle reciprocation, a loop taker journaled in said supporting arm and cooperating with said needle in the formation of stitches, a needle thread loop seizing beak provided on said loop taker, a pinion rotatable with said loop taker, a gear segment fixed on said frame in mesh With said pinion, and means driven by said actuating mechanism for imparting oscillatory movement to said loop taker supporting arm to move said loop taker beak in an epitrochoidal path in timed relation with said needle reciprocation.

2. In a sewing machine having a frame, a thread carrying needle endwise reciprocable in said frame, an actuating mechanism carried in said frame and operably connected to impart reciprocatory movement in an endwise path to said needle, a loop taker supporting arm pivotally mounted in said frame for oscillatory movement transversely of said path of needle reciprocation, a loop taker journaled in said supporting arm and cooperating with saidneedle in the formation of stitches, a pinion rotatable coaxially with said loop taker, a needle thread loop seizing beak provided on said loop taker at a distance from the axis of said loop taker which is greater than the pitch circle of said pinion, a gear segment fixed on said frame in mesh with said pinion, and means driven by said actuating mechanism for imparting oscillatory movement to said loop taker supporting arm to move said loop taker beak in a prolate epitrochoidal path in timed relation with said needle reciprocation.

3. In a lockstitch sewing machine having a frame, a thread carrying needle endwise reciprocable in said frame, an actuating mechanism carried in said frame and operably connected to impart reciprocatory movement in an endwisepath to said needle, a circular shuttle formed with a needle thread loop seizing beak cooperating with said needle in the formation of stitches, means driven by said actuating mechanism for reciprocating said shuttle bodily in a path transversely of said needle path, and means responsive to said bodily reciprocation for simultaneously rotating said circular shuttle to impart an epitrochoidal path of motion to said needle thread loop seizing beak.

4. In a lockstitch sewing machine having a frame, a thread carrying needle endwise reciprocable in said frame, an actuating mechanism carried in said frame and operably connected to impart reciprocatory movement in an endwise path to said needle, a circular shuttle formed with a needle thread loop seizing beak cooperating with said needle in the formation of stitches, a thread carrying bobbin journaled in said shuttle, bobbing thread tensioning means carried on said shuttle including a bobbin thread guiding means spaced from said beak from which guiding means the bobbin thread issues from the shuttle, means driven by said actuating mechanism for reciprocating said shuttle bodily in a path transversely of said needle path, and means responsive to said bodily reciprocation for simultaneously rotating said circular shuttle to impart epitrochoidal paths of motion to said needle thread loop seizing beak and to said bobbin thread guiding means.

5. In a lockstitch sewing machine as set forth in claim 4 in which said thread carrying bobbin includes a hub and at least one circular flange, and in which said bobbin thread tensioning means include a brake lever, means defining a pivotal axis on said shuttle for turning movement of said brake lever, spring means biasing said brake lever into engagement with said bobbin flange, and bobbin thread engaging means on said lever adjacent to said bobbin thread guiding means on said shuttle, whereby tension in the bobbin thread can exert a force on said brake lever in opposition to said spring means when said tensioned bobbin thread is directed from said thread guiding means in a direction substantially perpendicular to the pivotal axis of said brake lever.

6. In a lockstitch sewing machine as set forth in claim 4 in which said means driven by said actuating mechanism for reciprocating said shuttle bodily in a path transversely of said needle path positions said shuttle adjacent to said needle path at one extremity of said reciprocation and remote from said needle path at the other extremity of said reciprocation, and in which said bobbin thread guiding means is disposed when the shuttle occupies a position at the extremity of said reciprocation which is remote from said needle path so as to direct the bobbin thread toward said needle path in a direction substantially perpendicular to the said pivotal axis of said brake lever.

7. In a sewing machine having a frame, a thread carrying needle reciprocable in an endwise path in said frame, a loop taker cooperating with said needle in the formation of stitches, a needle thread loop seizing beak provided on said loop taker, means shiftably supporting said loop taker in said frame for movement of said loop seizing beak in an epitrochoidal path extending transversely of said path of needle reciprocation, actuating mechanism for said needle and loop taker comprising a single rotary actuating member journaled in said frame, a lever in said frame, means driven by said actuating member for oscillating said lever, linkage operatively connecting said lever with said needle, and linkage operatively connecting said lever with said shiftable loop taker supporting means.

8. In a lockstitch sewing machine having a frame, a thread carrying needle recipro-cable on said frame on an endwise path, a shuttle supporting arm pivotally mounted in said frame for oscillatory motion transversely of said needle path of reciprocation, a circular shuttle journaled in said supporting arm and cooperating with said needle in the formation of stitches, a needle thread loop seizing beak provided on said shuttle, a pinion rotatable with said shuttle, a gear segment fixed on said frame and in mesh with said pinion, and actuating mechanism for said needle and shuttle comprising a single rotary actuating member journaled in said frame, a lever fulcrumed in said frame, means driven by said actuating member for oscillating said lever, linkage operatively connecting said lever with said needle, and linkage operatively connecting said lever with said shuttle supporting arm to move said shuttle beak in an epitrochoidal path in timed relation with said needle reciprocation.

9. In a sewing machine having a frame, a thread carrying needle endwise reciprocable in said frame, and actuating mechanism carried in said frame and operably connected to impart reciprocatory movement in an endwise path to said needle, a loop taker cooperating with said needle in the formation of stitches, a needle thread loop seizing beak provided on said loop taker, a loop taker supporting arm shiftably mounted in said sewing machine frame, means supporting said loop taker in said supporting arm for turning movement therein, and means driven by said actuating mechanism in timed relation with said needle reciprocation for shifting said loop taker supporting arm to move said loop taker body substantially transversely of said needle path of reciprocation and for simultaneously imparting turning movement to said loop taker relatively to said supporting arm thereby moving said loop seizing beak in a non-circular curvilinear path.

References Cited UNITED STATES PATENTS 975,155 11/1910 Pepperling 112186 1,413,274 4/1922 Horat 112-184 1,691,242 11/ 1928 Greenwood 112-184 1,756,699 4/1930 Parkes 1l2-184 1,996,290 4/1935 Gunther 112-184 3,242,891 3/1966 Bialy 112184 FOREIGN PATENTS 669,252 12/ 1938 Germany.

670,447 1/ 1939 Germany.

HERBERT F. ROSS, Primary Examiner. 

